Method for the recognition of the synchronised position and the end of the synchronisation process in automatic gearbox

ABSTRACT

A method for recognition of the sychronization position and the end of the synchronization operation in an automated shiftable transmission with an electromotive shift actuator is disclosed, which is characterized in that the rotational speed of the shift actuator is detected and the synchronization position, as will as the end of the synchronized operation,is determined based upon the change of the rotational speed.

[0001] The present invention relates to a method for the recognition of the synchronization position and the end of the synchronization operation of an automatic shiftable transmission according to the preamble of claim 1.

[0002] Shiftable transmissions for motor vehicles have long been known in many different forms, in the past, a shiftable transmission was primarily understood to be a manually-shiftable transmission, in which the driver of a motor vehicle equipped with this type of shiftable transmission selects the shift path and performs the gear shift operation by hand via a shift lever. In addition to these manually-shiftable transmissions, it has also been known in the meantime to use automated shiftable transmissions when the operation of selecting and shifting the selected gear stage is executed, for example, according to programmed control by actuators provided in the shiftable transmission.

[0003] During operation, an automated shiftable transmission of this kind is subjected to normal wear and tear on its component parts, e.g., the synchronizing means, which wear and tear can lead to displacement of the middle synchronization position. By the middle synchronization position, a mean position value during the synchronization operation is meant, as the blocking position of the synchronizing means can vary somewhat from shift operation to shift operation, because the shift sleeve can engage in the synchronizer ring differently and unpredictably from shift operation to shift operation.

[0004] However, accurate knowledge of the synchronization position is important, as the synchronization position should be quickly reached by the shift actuator in order to shorten the shift time, and the shift actuator should also quickly arrive at its end position at the end of the synchronization operation.

[0005] When the shift actuator reaches the synchronization position, the synchronizing means exerts a blocking effect on the shift actuator as a result of the synchronization operation, which leads to an increase in the load current of the actuators. It has already been known to detect the start of the synchronization by this increase in the load current.

[0006] However, detecting the load current is comparatively complicated and expensive and furthermore, can only produce a result with regard to a change of the synchronization position within the bounds of a continuous determination of the actuator position, as the position of the actuator when the load current increases must be known.

[0007] Thus, the object of the present invention is to provide a method, in which in a less expensive manner a change of the synchronization position and the end of the synchronization operation can be recognized.

[0008] The invention is achieved by the solution of this object in accordance with the features of claim 1. Advantageous embodiments of this are described in the additional claims.

[0009] According to the invention, a method for the recognition of the synchronization position and the end of the synchronization operation of an automated shiftable transmission having an electromotive shift actuator is provided, in which the rotational speed of the shift actuator is detected and the synchronization position, as well as the end of the synchronization operation, is determined from a change in the rotational speed.

[0010] By detecting the rotational speed of the shift actuator over time, it is possible to determine the path through which the shift actuator has moved so that, even without a continuous determination of the actuator position, according to this method it is possible to determine the synchronization position that is reached when the rotational speed of the shift actuator undergoes a predetermined threshold value change within a predetermined time interval.

[0011] The rotational speed can be detected by means of sensors that generate a predetermined number of pulses per revolution of the actuator shaft. By measurement of the pulse frequency and/or the timed pulse interval, it is possible to determine the rotational speed. It is also possible to determine geometric intervals by addition of the pulses.

[0012] Therefore, according to the invention, if it is determined that the rotational speed of the shift actuator has experienced a clear decline within a certain time interval, then it is concluded that the synchronization position has been reached.

[0013] During the synchronization operation, the synchronizing means exerts a blocking effect against any further movement of the shift actuator, which blocking effect is released at the end of the synchronization operation, and thus results in an increase in the rotational speed of the shift actuator.

[0014] Because the wear behaviour of the automated shiftable transmission can also lead to gear-specific changes in the shift characteristics, it is proposed according to the invention that the synchronization position and the end of the synchronization operation is determined independently for each gear stage of the automated shiftable transmission.

[0015] With the method according to the invention, it is therefore possible to identify gear-specific changes of the synchronization position and also to determine the gear-specific end of the synchronization operation.

[0016] Changes in the synchronization position of the relevant gear stages of the automated shiftable transmission during operation can therefore be taken into account by determining the synchronization position and by using this synchronization position as the assumed target synchronization position during the next gear change operation for the relevant gear stage in order to control the shift actuator. Similarly, by continuously monitoring the rotational speed of the shift actuator, it is possible to determine whether the synchronization operation has concluded, which can be ascertained, e.g. by a parabolic or quite general progressive increase in the rotational speed of the shift actuator over time.

[0017] In this way, it is therefore possible to determine on the one hand changes in the synchronization position in the direction towards the neutral position of the transmission or away from same, and on the other hand, also changes in the time duration of the synchronization operation, so that for example an increase in the current supply to the shift actuator, even before the conclusion of the synchronization operation, leads only to an insignificant acceleration of the shift actuator, and thus change of its rotational speed, so that it can be concluded from this that the synchronization operation has not yet ended. This knowledge can then be used during a subsequent gear change operation and a corresponding synchronization so as to accordingly delay the start of the increase of the current supply to the shift actuator, thereby not stretching the shift elasticity.

[0018] Conversely, if the end of the synchronization is known, it is therefore possible to increase the load current for the shift actuator without any further delay, so that the end position of the shift actuator on its travelling path to the engaged gear stage can be rapidly reached, which leads to a shortening of the travelling time of the shift actuator to reach the end position and thus to a shortening of the shift time.

[0019] It is thereby proposed according to the invention that the determined synchronization position is stored in a memory device and, at the next gear change operation, is then read out from the memory device as the target synchronization position for movement to the synchronization position effected by the shift actuator. For this purpose, a volatile memory can be provided in which the synchronization position is stored during operation of the shiftable transmission. Therefore, the gear-specific last synchronization positions, which are in use when the automated shiftable transmission equipped motor vehicle is stopped, can be utilized during the next vehicle driving operation, by writing these values in a non-volatile memory after stopping the vehicle, e.g., which is controlled by an ignition signal, and then reading out these values again during the next vehicle start-up and storing these values in the volatile memory.

[0020] The stored synchronization position is thereby up-dated with the synchronization position determined by this method when the stored synchronization position deviates from the determined synchronization position, so that changes in the synchronization position do not lead to a change in the shift characteristics of the transmission.

[0021] It is thereby proposed according to the invention that the up-dating is performed when the determined synchronization position changes, as compared with the stored synchronization position, for the individual gear stages of the automated shiftable transmission in different directions in relation to the neutral position. In other words, this means that an up-date is performed when the determined synchronization position, e.g., of the first gear changes towards the neutral position and e.g., of the third gear changes in a direction away from the neutral position In case of a change of the gear-specific synchronization position for all gears in the same direction, it can be assumed that the shift pattern has moved altogether and therefore, an adaptation of the synchronization position for the individual gear stages is not necessary.

[0022] According to a further development of the method according to the invention, it is hereby proposed that the up-date is performed only when the shiftable transmission has warmed up to its operating temperature, wherein a sensor is provided on the shiftable transmission in order to ascertain the temperature thereof and/or a predetermined operating time of the shiftable transmission is awaited. An allowance is thereby made of the fact that, if the operating parameters of the automated shiftable transmission do not remain substantially the same, such as e.g. the oil viscosity within the transmission, an adaptation mistake could result, which will be avoided in this way.

[0023] The stored synchronization position is used to control the shift actuator, so that the shift actuator reduces the speed of the travelling movement of the shift elements in the shiftable transmission before the target synchronization position. A large mechanical strain on the shift actuator and shift elements is thereby avoided.

[0024] It can also be provided with this method that the change in the synchronization position in relation to the neutral position is determined and, upon exceeding a predetermined change threshold value, an action notification is issued. This can be, e.g., a corresponding entry in the fault memory of the vehicle so that during the next vehicle visit to the mechanic's garage, suitable remedial measures can be performed, such as e.g., worn synchronizing rings can be replaced in the transmission.

[0025] The invention will now be explained in further detail with reference to the drawings in which:

[0026]FIG. 1 shows a graphic illustration of the position of the shift actuator when engaging a gear while the transmission is synchronizing;

[0027]FIG. 2 shows an illustration to explain the identification of displacements of the synchronization position;

[0028]FIG. 3 shows an illustration for explaining a displacement of the shift pattern; and

[0029]FIG. 4 shows an illustration for explaining the importance of the synchronization position.

[0030] In FIG. 1 of the drawings, the curved lines 1 and 2 each designate the shift operation when a “neutral-distant” synchronization position is present, while the curved lines 3 and 4 each designate the shift operation for a “neutral-close” synchronization position. According to the term “neutral-distant,” a change in the synchronization position, as determined by the controller, away from the neutral position is meant and, according to the term “neutral-close,” a change in the determined position in a direction towards the neutral position is correspondingly meant.

[0031] As can be readily seen, the shift actuator illustrated over time is at first moved linearly and is then braked towards the synchronization position or synchronization operation, which exerts a blocking effect against further movement during the synchronization operation. Therefore, this means that the shift actuator is braked and becomes practically stationary until time point A, wherein it continues to exert a force, however, that leads, after time point B, to an acceleration of the shift actuator, and thereby an increase in the rotational speed.

[0032] As can be seen from the curved line shown by 1, a parabolic-form course is provided with a high acceleration, whereas the curved line 2 represents a course with a reduced acceleration, as the beginning of the controlled acceleration of the shift actuator according to the curved line 2 would be selected too early, in which case the blocking effect of the synchronization is still being exerted and thus only a slight acceleration is provided. By monitoring the rotational speed of the shift actuator during a next following shift operation, a course can therefore be attained according to the curved line 1, by which the controlled acceleration starts later when the blocking action of the synchronization has ceased. This leads to an overall faster shift operation, because the acceleration is greater, and also to a reduction of the mechanical strain on the shift actuator and synchronizing means, because the shift actuator does not work against synchronization while the synchronizing means is still blocking.

[0033] The curved lines 3 and 4 of FIG. 1 show similar conditions with a synchronization position closer to the neutral position. By a detection of the end of the synchronization operation, it is thus also possible with a synchronization position lying closer to the neutral position to attain a change in the position of the shift actuator, as expressed in the curved line 3, and thus to a reduction in the shift time. In comparison, the curved line 4 shows again, for clarity, a premature assumed end of the synchronization operation with a corresponding lengthening of the time period until reaching the end position of the shift actuator, i.e., the “gear engaged” position.

[0034] In two examples, FIG. 2 of the drawing shows that a change in the synchronization position can be concluded.

[0035] In the example illustrated in Case 1, the actual synchronization position (ST) lies farther away from neutral than the synchronization position (SV) utilized or assumed by the controller. This is concluded from the fact that the stationary position (SS) was determined to be above the utilized synchronization position SV. This stationary position (SS) is also shown in FIG. 1 of the drawing and corresponds to the position of the shift actuator after braking (horizontal curved line) and is utilized during the synchronization operation.

[0036] At the end of the synchronization operation, a large acceleration (A>) is apparent, which corresponds in FIG. 1 to the steep position parabola, so that an adaptation, i.e. a correction of the assumed synchronization position (SV) utilized by the controller, is appropriate. This determined synchronization position can then be stored as the new synchronization position in the memory of the controller,

[0037] Case 2 shows that the actual synchronization position (ST) lies closer to neutral than the assumed synchronization position (SV). A low acceleration (A<) is present. The assumed synchronization position (SV) was assumed to be above the stationary position (SS) and the actual synchronization position (ST), the actuator still has however worked against the blocking effect of the synchronizing means. An adaptation in the direction close to neutral is appropriate.

[0038]FIG. 3 of the drawing shows an illustration to explain a displacement of the shift pattern. In relation to the neutral position, a change of the synchronization position for each forward gear has occurred in the same direction, which direction change is shown by the upwardly directed arrows, so that from this, it can be concluded that the shift pattern has moved altogether and that an adaptation by the controller is thus not necessary.

[0039] Lastly, FIG. 4 of the drawing serves to explain the importance of the synchronization position. The controller uses the assumed synchronization position SV to brake the shift actuator just before reaching the stationary position SS. This serves to arrive at the stationary position as fast as possible, thereby shortening the time for the gear change operation, without however “moving into” the synchronization position with a still high speed of the shift actuator, as this would result in a “bounce back” of the shift actuator, due to the blocking effect of the synchronizing means.

[0040] If the assumed synchronization position SV used by the controller is located neutral-distant, then no braking takes place and the shift actuator must absorb the forces that originate from the direct contact with the synchronizing means, which leads to the aforementioned bounce-back. With a too neutral-close assumed synchronization position SV, the result is a premature braking of the shift actuator. The shift actuator then “creeps” slowly to the stationary position SS. The duration of the drive force interruption during a gear change operation increases, which has the effect of shift comfort reduction. With a correctly assumed synchronization position SV (as a result of an adaptation at the previous shift operation), the high mechanical strain on the shift actuator, on the one hand, ceases and on the other hand, a short time results for the gear change operation and thus short drive force interruption.

[0041] For further features of the invention, which are not explained in more detail above, reference is expressly made to the claims.

[0042] The patent claims filed with the application are proposed wordings without prejudice to obtain broader patent protection. The applicant reserves the right to claim further combinations of features disclosed until now only in the description and/or drawings.

[0043] References made in the sub-claims refer to the further design of the subject of the main claim through the features of the relevant sub-claim; they are not to be regarded as dispensing with obtaining an independent subject protection for the combination of features of the sub-claims referred to.

[0044] Since the subjects of the sub-claims can form independent inventions compared with the prior art known on the priority date the applicant reserves the right to make them the subject of independent claims or divisional declarations. They can also contain independent inventions that have a configuration independent of the subjects of the preceding sub-claims.

[0045] The embodiments are not to be regarded as restricting the invention. Rather, numerous modifications and amendments are possible within the scope of the present disclosure, in particular, those variations elements and combinations and/or materials that can be derived by the expert as a solution of the object, for example, by combinations or modifications of individual features, elements or method steps contained in the drawings and described in connection with the general description and embodiments as well as claims, and by combinable features that lead to a new subject or new method steps or sequence of method steps, insofar as they relate to manufacturing, test and work methods. 

1. Method for the recognition of the synchronization position and the end of the synchronization operation of an automated shiftable transmission provided with an electromotive shift actuator characterised in that the rotational speed of the shift actuator is detected and the synchronization position, as well as the end of the synchronization operation, is determined from the change of the rotational speed.
 2. Method according to claim 1, characterised in that, the synchronization position is determined from a reduction of the rotational speed of the shift actuator.
 3. Method according to claim 1, characterised in that, the end of the synchronization operation is determined from an increase of the rotational speed of the shift actuator.
 4. Method according to one of claims 1 to 3, characterised in that, the synchronization position and the end of the synchronization operation are determined for each gear stage of the automated shiftable transmission.
 5. Method according to one of claims 1 to 4, characterised in that, the detected synchronization position is stored in a memory device and, at the next gear change operation, is read out from the memory device as target synchronization position for movement to the synchronization position effected by the shift actuator.
 6. Method according to claim 5, characterised in that, the stored synchronization position is up-dated with the determined synchronization position when it deviates from the determined synchronization position.
 7. Method according to claim 5 or 6, characterised in that, the up-date is performed when the determined synchronization position, as compared with the stored synchronization position for individual gear stages of the automated shiftable transmission, changes in different directions in relation to the neutral position.
 8. Method according to one of claims 5 to 7, characterised in that, the up-date is only performed when the shiftable transmission has warmed up to its operating temperature, wherein a sensor is provided on the shiftable transmission in order to determine the temperature thereof and/or a predetermined operating time of the shiftable transmission is awaited.
 9. Method according to one of claims 1 to 8, characterised in that, the shift actuator is controlled by the stored synchronization position so that the shift actuator reduces the speed of the travelling movement of the shift elements in the shiftable transmission prior to the target synchronization position.
 10. Method according to one of claims 1 to 9, characterised in that, the change in the synchronization position in relation to the neutral position is determined and, upon exceeding a predetermined change threshold value, an action notification is issued.
 11. Use of the method according to one of claims 1 to 10 for adaptation of the synchronization position and for shortening the travelling time of the shift actuator for reaching the end position. 